Dry kiln



May 1930.

M. B. HA LL DRY KILN Fi led Sept. 7, 1927 [ma ma] 00ZmB.H aZZ,

Patented May UNITED STA PATENT, omce mucous: 3. mm, or roxn'oao, massacnusn'rrs, ASSIGNQR To run roxnono oomrun, 011 302.3030, nessacnusnrrs, acoarona'rron or massacnusnr'rsv DBYKILN= Application filed September 7,1927, "serial in. 211977.

festing the temperature and humidity. conditions therein to permitdesired observation or control of the drying process. My invention will be well understood from the fol-.

lowing description taken in connection with the accompanying drawings, wherein I have shown diagrammatically, partly in longitudinal section with parts broken away, a lumber kiln with which is associated in automatic humidity controllin mechanism ex-- to Bristol 1,195,334, dated August 22, 1916,

em li the rinciles my invention.

l efii' r i g to the dr wings, I have there illustrated in diagrammatic section a kiln 3 in which are disposed the trucks 5 carrying lumber to be dried. The humidity conditions in the kiln may besuitably controlled, herein by the joint action of the heating means, such as steam pipes 7, and moisture-supplyingmeans, such as the spray pipe 9.

Theoretically and desirably the condition 1 of the air circulating in a kiln of this character should be uniform throughout. However, because there may be a space between the several trucks on which the lumber 1s piled, or because of uneven stacking on the v trucks themselves or non-uniformity ofthe material being dried, the conditions at different points of the kiln may considerably vary. The object of the present invention is to provide for controlling the humidity conditions in response 'to the conditions in some part of the kiln in which one of the controlling factors is at a maximum wherever this part of the kiln may be located, and thus to insure that no portion of the charge shall be subjected to conditions which would be detrimental to its proper drying.

By way of example I have herein shown in a very diagrammatic form suitable automatic controlling means, embodying suitable servomotors 11 and 13 respectively controlling admission valves in the steam line leading to the heater 7 and the spray pipe 9.

These may be pneumatically operated through the action of control heads 15 and 15 each governed by a suitable cdntrol couple which, as in the case of head 15, may embody a nozzle member 17 having an exhaust ort and a valv'e s'eat'land a cooperatingva-ve19. .;The"constructi0n of this con trolhng mechanism is shown herein in a dia-- grammatic manner onlyiand may in practice be substantially asshown in the patentto' D1xon 1,582,868, dated April 27, 1926. The

valve seat member 17 maybe adjusted, conveniently' manually, and the cooperating valve 19 may be automatically moved in rela tion thereto by means of a suitable thermometric responsive element 21 which may be a'helical tube of the type shown' in the patent adapted to be distorted by vapor pressure internally thereof to operate the valve 19.

For controlling the spray pipe 9 the helical tube 21 may be connected by means of a finegage or capillary transmission tube 23 with a wet bulb device inside the comprising a suitable bulb or liquid-containing reservoir 25 which has applie thereto the textile cover 27 dipping into a water reservoir 29 or some equivalent device. The tube 21 thus responds to the wet bulb temperature in well known manner. The tube 21, which is de signed to operate in accordance with the dry bulb temperature within the kiln, ma be connected withthe interior of the kiln y a similar capillary transmission tube 31- but instead of utilizing an enlargedliquid-containing bulb within the kiln this fine-gage tube is extended at 33 throughout the length of the kiln and exposed to the temperature conditions therein. The total volume of the capillary tube is not substantially in excess of that of the ordinary bulb and it in itself constitutes the bulb bymeans of which the dry bulb temperature, so-called, is rendered effective to operate the tube 21.

By the means described the element 21 and consequently the action of theservomotor 11 which is governed thereby depends upon the maximum temperature in the kiln in Whatever zone the maximum may occur. By maximum temperature in the instance illustrated is to be understood the maximum temperature of the air at any given zone longitudinally. of the kiln at the location of the capillary bulb 33.. It will be understood that the pipe 33 being full of vaporizable liquid,

heat applied at a certain zonethereof will vaporize the'same causing a pressure which is the function of the temperature. This pressure acting on the liquid in zones of less 7 heat will retain the liquid in these parts as liquid. That is, in these zones the liquid cannot boil. A pressurecorresponding to the maximum temperature isthus transmitted to the helical tube 21 and governs the operation of the control couple 1719 and thus throu h the control head 15, servomotor 11 and t e heating device 7 It w1ll be understood that, While I have herein shown the conditions in the kiln as automatically controlled by the action of the wet and dry bulbs, these might operate indicating or recording instruments manifesting the conditions in the kiln and that control, if necessary, might be efiected manually in accordance with the readings of such instruments. If the controllin instruments are of the type disclosedin the ixon patent referred to, obviously they also serve to record and indicate the values of the variables.

I have described in detail the illustrated diagrammatic disclosure of a certain embodiment of my invention-in order that the rinciples underlying the same might be we understood. Obviously the mechanism utilized may be I considerably varied from what is shown and what I claim as new and desire to secure by Letters Patent I shall express in the following claim.

Claim:

A dry kiln having means for manifesting humidity conditions therein comprising pressure-operated elements adapted to'respond to the wet and dry bulb temperature respectively and including a fine-ga e tube filled with liquid which vaporizes wit in the range of temperatqre which the kiln has in use and extending substantially throughout the length of theinterior of the kiln and in communication with the second of said elements and constituting in itself the source of actuating pressure therefor.

In testimony whereof, I have signed my name to this specification. MALCOLM B. HALL. 

